A power supply circuit of the present invention includes a voltage boosting capacitor, a first switch, a second switch, an addition comparison circuit, and a control circuit. The first switch charges the voltage boosting capacitor by applying a first voltage thereto. The second switch connects a second voltage serially to the voltage boosting capacitor that is already charged, thereby boosting the voltage therein. The addition comparison circuit adds up the voltage of the voltage boosting capacitor and the second voltage and compares the comparison result, with a predetermined threshold value. The control circuit controls the on/off state of the first switch according to the comparison result of the addition comparison circuit.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A voltage boosting power supply circuit, comprising: an output node which outputs an output voltage to a load circuit; a voltage boosting capacitor; a first switch which applies a first voltage to said voltage boosting capacitor, to charge said voltage boosting capacitor; a second switch which connects a second voltage serially to said voltage boosting capacitor to boost a charging voltage of said voltage boosting capacitor; a third switch which discharges a boosted charging voltage of said voltage boosting capacitor, an end of said third switch being coupled between said voltage boosting capacitor and said first switch, another end of said third switch being coupled to said output node; an extraction switch which has one end coupled between said voltage boosting capacitor and the third switch, and is controlled according to charging said voltage boosting capacitor to extract said charging voltage of said voltage boosting capacitor; an addition comparison circuit which couples to another end of said extraction switch, and compares, a sum of said charging voltage of said voltage boosting capacitor and said second voltage, with a predetermined threshold value to generate a result of said comparison; and a control circuit which controls an on/off state of said first switch according to said result of comparison during said charging said voltage boosting capacitor.
2. The voltage boosting power supply circuit according to claim 1 , wherein said control circuit controls said on/off states of said first and second switches so that charging and discharging of said voltage boosting capacitor is alternated repetitively synchronously with a voltage boosting clock; and wherein said control circuit, when said sum exceeds said predetermined threshold value, stops said charging by controlling said first switch.
3. The voltage boosting power supply circuit according to claim 1 , wherein said addition comparison circuit includes: an addition circuit which couples to said another end of said extraction switch, and adds up said charging voltage of said voltage boosting capacitor and said second voltage to generate said result of said addition; a comparison circuit which compares said result of addition with said predetermined threshold value to generate said result of said comparison.
4. The voltage boosting power supply circuit according to claim 1 , wherein an input terminal of said addition comparison circuit couples between said third switch and said output node, and wherein said addition comparison circuit further adds up said boosted charging voltage while said voltage boosting capacitor is charged and compares a result of said addition with said predetermined threshold voltage.
5. The voltage boosting power supply circuit according to claim 4 , further comprising: a second voltage boosting capacitor; a fourth switch which applies said first voltage to said second voltage boosting capacitor, to charge said second voltage boosting capacitor; a fifth switch which connects a third voltage serially to said second voltage boosting capacitor that is already charged, thereby boosting a voltage of said second voltage boosting capacitor; and a second extraction switch which extracts the voltage of said second voltage boosting capacitor that is being charged, wherein said second voltage boosting capacitor having a voltage already boosted outputs said second voltage through said second switch, and wherein said addition comparison circuit compares a sum of said voltage of said voltage boosting capacitor that is being charged, said voltage of said second voltage boosting capacitor that is being charged, and said third voltage, with a predetermined threshold value.
6. The voltage boosting power supply circuit according to claim 5 , further comprising: a third voltage boosting capacitor; a sixth switch which applies said first voltage to said third voltage boosting capacitor while said voltage boosting capacitor is discharged, thereby charging said third voltage boosting capacitor; a seventh switch which connects said second voltage serially to said third voltage boosting capacitor that is already charged, thereby boosting said third voltage boosting capacitor; and a third extraction switch which extracts said voltage of said third voltage boosting capacitor that is being charged, and wherein said addition comparison circuit compares a sum of said voltage of said voltage boosting capacitor or said third voltage boosting capacitor, whichever is being charged, and said second voltage, with said predetermined threshold value, and outputs a result of said comparison.
7. A liquid crystal display panel driving apparatus, comprising: a voltage boosting power supply circuit according to claim 1 ; and a display control unit for supplying a voltage boosting clock synchronizing with a display clock to said voltage boosting power supply circuit.
8. The voltage boosting power supply circuit as claimed in claim 1 , further comprising: a resistance element which supplies a voltage to said voltage boosting capacitor and limits a charging current upon charging said voltage boosting capacitor.
9. The voltage boosting power supply circuit as claimed in claim 8 , wherein said resistance element is provided between said first switch and said voltage boosting capacitor.
10. The voltage boosting power supply circuit according to claim 8 , wherein said resistance element comprises an on-resistance assumed when said first switch is turned on and limits said charging current upon charging said voltage boosting capacitor.
11. The voltage boosting power supply circuit according to claim 8 , further comprising a second comparison circuit which compares said first voltage with a predetermined threshold value, and outputs a second comparison result, and wherein said power supply circuit changes a resistance value of said resistance element according to said second comparison result.
12. The voltage boosting power supply circuit according to claim 11 , wherein said resistance element includes a first resistor and a second resistor, and wherein said power supply circuit changes the resistance value of said resistor element by switching between said first resistor and said second resistor according to said second comparison result.
13. The voltage boosting power supply circuit according to claim 12 , wherein said first switch includes a first transistor and a second transistor, each having an on-resistance value that differs between said first and second transistors, and wherein said first resistor comprises an on-resistance for said first transistor, and said second resistor comprises an on-resistance for said second transistor.
14. The voltage boosting power supply circuit according to claim 8 , wherein a node provided at a ground side of said voltage boosting capacitor is grounded through an independent line separated from a common line provided in a circuit for supplying a ground voltage.
15. The voltage boosting power supply circuit according to claim 1 , wherein said predetermined threshold value comprises a voltage corresponding to said first voltage.
16. A boosted voltage control method, comprising: outputting an output voltage from an output node to a load circuit; applying a first voltage to a voltage boosting capacitor, to charge said capacitor; connecting a second voltage serially to said voltage boosting capacitor that is already charged, to boost a charging voltage of said voltage boosting capacitor; discharging a boosted charging voltage of said voltage boosting capacitor; extracting said charging voltage of said voltage boosting capacitor based on the charging of said voltage boosting capacitor; adding up a voltage of said voltage boosting capacitor and said second voltage, during charging said voltage boosting capacitor; comparing a result of addition with a predetermined threshold value, during charging said voltage boosting capacitor; and stopping charging of said voltage boosting capacitor according to a result of comparison.
17. The boosted voltage control method according to claim 16 , wherein said charging and said connecting are repeated alternately synchronously with a voltage boosting clock inputted externally, and wherein said stopping includes stopping charging of said voltage boosting capacitor when said result of addition exceeds said predetermined threshold value in said charging.
18. The boosted voltage control method according to claim 16 , further comprising extracting said voltage of said voltage boosting capacitor that is being charged.
19. The boosted voltage control method according to claim 16 , further comprising: discharging a charge from said voltage boosting capacitor having a voltage already boosted; and extracting an output voltage of said voltage boosting capacitor upon discharging, wherein said adding includes adding up said output voltage while said voltage boosting capacitor is being charged.
20. The boosted voltage control method according to claim 16 , further comprising: applying said first voltage to a second voltage boosting capacitor, thereby charging said second voltage boosting capacitor; connecting a third voltage serially to said second voltage boosting capacitor that is already charged, thereby boosting the voltage of said second capacitor; and outputting said voltage of said second voltage boosting capacitor having a voltage already boosted as said second voltage, wherein said adding includes adding said voltage of said voltage boosting capacitor that is being charged, said voltage of said second voltage boosting capacitor that is being charged, and said third voltage, and outputting a result of said addition.
21. The boosted voltage control method according to claim 20 , further comprising: applying said first voltage to a third voltage boosting capacitor upon discharging said voltage boosting capacitor, thereby charging said third voltage boosting capacitor; connecting said second voltage serially to said third voltage boosting capacitor that is already charged, thereby boosting the voltage of said third voltage boosting capacitor; and extracting said voltage from said third voltage boosting capacitor that is being charged, wherein said adding includes adding up said voltage of said voltage boosting capacitor or said third voltage boosting capacitor, whichever is being charged, and said second voltage, and outputting a result of said addition.
22. The boosted voltage control method as claimed in claim 16 , wherein said first voltage is applied through a resistance element to said voltage boosting capacitor.
23. The boosted voltage control method according to claim 22 , further comprising: comparing said first voltage with said predetermined second threshold value, then outputting a result of said comparison, wherein said charging includes changing a resistance value of said resistance element according to said result of second comparison.
24. The boosted voltage control method according to claim 23 , wherein said resistance element includes a first resistor and a second resistor, and wherein said charging includes changing said resistance value of said resistance element by switching between said first resistor and said second resistor according to said second comparison result.
25. The boosted voltage control method according to claim 22 , further comprising grounding a node provided at the ground side of a voltage boosting capacitor through an independent line separated from a common line provided in a circuit for supplying a ground voltage.
26. A voltage boosting power supply circuit, comprising: means for outputting an output voltage from an output node to a load circuit; means for applying a first voltage to a voltage boosting capacitor, to charge said capacitor; means for connecting a second voltage serially to said voltage boosting capacitor that is already charged, to boost a charging voltage of said voltage boosting capacitor; means for discharging a boosted charging voltage of said voltage boosting capacitor; means for extracting said charging voltage of said voltage boosting capacitor based on the charging of said voltage boosting capacitor; means for, during charging said voltage boosting capacitor, comparing a sum of the voltage of said voltage boosting capacitor and said second voltage, with a predetermined threshold value, and outputting a result of said comparison; and means for controlling an on/off state of said means for applying according to said result of comparison during said charging said voltage boosting capacitor.
27. The voltage boosting power supply circuit as claimed in claim 26 , further comprising means for resisting a charging current upon charging said voltage boosting capacitor.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 14, 2008
June 4, 2013
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